This disclosure relates to the determination of the polysaccharides found in Dendrobium houshanense and the effect of administration of the polysaccharides to trigger immunomodulatory activity, including the up regulation of beneficial cytokines.
Dendrobium huoshanense is a precious and endangered medicinal plant that originated in China. In this study, detailed structures of the polysaccharides extracted from the leaf and stem cell walls and mucilage of D. huoshanense are determined by using various techniques, including chromatographic, spectroscopic, chemical and enzymatic methods. The composition of monosaccharides and their linkages in the cell wall and mucilage were deduced. In addition to the previously reported mannose, glucose and galactose, new monosaccharide constituents of rhamnose, fucose, arabinose, xylose, galacturonic acid, glucuronic acid, 4-O-methylglucouronic acid and 2-O-acetylmannose are firstly found in D. huoshanense. The pectic fractions of leaf and stem are found to contain mostly homogalacturonan (HGA) and galactomannan, with a smaller proportion of rhamnogalacturonan (RG). The alkali extractable fractions are mainly composed of glucuronoarabinoxylans (GAXs), fucosylated xyloglucans (XGs) and glucomannan. In contrast, the mucilage polysaccharide extracted from stems and leaves is composed of 2- and 3-O-acetyl glucomannan. The mucilage polysaccharide exhibits specific functions in activating murine splenocytes to produce several cytokines including IFN-γ, IL-10, IL-6, and IL-1α, as well as hematopoietic growth factors GM-CSF and G-CSF. However, the deacetylated mucilage obtained from an alkaline treatment failed to induce cytokine production.
The extract of mucilage was further fractionated by chromatography on anion-exchange DEAE-cellulose and Sephacryl size-exclusion. The bioactive polysaccharide fraction B with an average molecular weight of ˜10 KDa is composed of β-(1→4)glucomannan having partial acetylation at the 2- and 3-positions of mannosides. The linkages of β-(1→4)-D-Glcp and β-(1→4)-D-Manp were elucidated by NOE spectrum and enzymatic methods. The chemical shifts of individual protons and carbons were assigned by using a series of 2D NMR spectroscopic techniques. This is the first study that provides clear evidence for the structure and activity relationship of the polysaccharides in D. huoshanense. 
Moreover, the fragments of oligosaccharide from Dendrobium huoshanense obtained by either acid hydrolysis or enzyme digestion, with or without chemical modification, also induce expression of beneficial protein, such as G-CSF that shows potential application of therapeutic uses.
Based on the above-mentioned discovery, bioactive mannose oligomers are prepared from high-molecular-weight mannans by using a combination of methods, including acid hydrolysis, enzyme digestion, extraction, dialysis, chromatography and chemical modification. The oligosaccharide containing six or more units of mannosides can induce expression of beneficial proteins, such as cytokines and growth factors in time- and dose-dependent manner.